In Hollywood, it's usually safe to assume that your waiter goes home at night to work on his screenplay, or that the answering-service operator is writing up a treatment that Universal is interested in ("No, really!"). But they're not the only frustrated screenwriters in town -- the others are just more celebrated and more visible. Take Robert Culp, who has starred on television ("I Spy," "The Great American Hero") and movies ("Bob and Carol and Ted and Alice," "Turk 182") but who really wants to be a screenwriter.

"For the past 10 years I've been involved in an ongoing process," Culp says of the low profile he's kept for most of the past decade. "I've been changing from an actor primarily involved in television to a writer primarily involved in motion pictures."

It hasn't been easy. As an actor, he's found movie executives notoriously gun-shy about casting performers who made their names on TV ("Turk 182" director Bob Clark, he says, had to fight to cast both Culp and "Vega$" star Robert Urich in the film), and as a writer he's found it even harder.

"It's 100 times worse to make the transition as a writer," says Culp, whose TV writing credits include the "I Spy" pilot episode. "It's like a guy who runs a drill press and loses a hand -- he's gotta learn how to be a chauffeur, because that's something he can do with one hand. It's a whole new set of rules. You have to regroove the synapses completely. It took a long time for me to unlearn how to write for television."

So far most of Culp's scripts have "come to naught." But he did write, direct and produce "Operation Breadbasket," a well-received documentary about black economics that he subsequently sold to ABC-TV at a time when he was most involved in politics. "After I made it," Culp says, "Jesse Jackson told me I'd do the most good for the movement and for myself if I returned to my profession, so I did."

And in 1972 he cowrote, directed and costarred -- with longtime colleague and friend Bill Cosby -- in "Hickey and Boggs." The first draft of that film's screenplay was also the first script that "48 Hrs." director Walter Hill ever sold, and he says Hill was "in shock" after seeing the film. "I talked to him for 10 minutes about how he mustn't be too upset," Culp says. "He stared at me like I was a tree, then just got up and walked away. And that was the last time I saw Walter, God bless him . . ."

Culp says he enjoyed working with Bob Clark on "Turk 182," which failed to generate much box-office enthusiasm in its opening weekend. Playing the beleaguered mayor of New York City, Culp even got to foil a pair of real-life New York hoods. Two armed bandits showed up in his mobile dressing room one day, and Culp told them the truth: Because of the lax security on most movie sets, actors almost never carry money when they're on location. The two settled for an autographed poster and left. What Culp didn't tell them -- and what Daily Variety forgot to mention when it printed the story several months ago -- was that in his dressing-room closet, in the pocket of his jeans, was $1,500 . . .

It wasn't nominated for best picture by the Academy, and the Golden Globes likewise passed on it, but "Beverly Hills Cop" has made an impact where it counts -- on the bottom line. The nationwide theater owners who make up the annual ShoWest convention, now under way in Las Vegas, gave the Eddie Murphy comedy its "Exhibition's Picture of the Year" award last night during an awards ceremony.

The film has gotten other recognition, too. Around town these days it's not unusual to hear the Beverly Hills Hotel jokingly referred to as the "Beverly Hills Cop Hotel" because of its high profile, under a pseudonym, in the film. And in one of the surest tests of a movie's clout, it has clearly inspired the plot for a CBS mini-series -- it's about a female detective from Laramie, Wyo., who investigates the murder of her best friend and winds up in (guess where?) Beverly Hills, working with a (guess who?) Beverly Hills cop. The title? "Beverly Hills Cowboy Blues" . . .

The forthcoming drama "The Mission" will again team Roland Joffe', a best-director nominee for "The Killing Fields," with producer David Puttnam, who won an Oscar for "Chariots of Fire" and is also up for "Killing Fields." Their star will be Robert De Niro, who didn't receive any nominations -- or even much respect -- for "Falling in Love" . . .

According to its publicity, "The Return of the Soldier" -- just opened in New York City and starring Alan Bates, Glenda Jackson, Julie Christie and Ann-Margret -- did quite well in a recent Los Angeles engagement. But a recent issue of the Hollywood Reporter pointed out a couple of problems: The film played L.A., all right, but only for a brief, Academy-qualifying run in December 1983. And not only did it fail to pick up any nominations, but it died a quick death at the box office . . .